The present invention pertains to connectors which are used to connect various other devices to subsea wellheads. The connector may be designed to connect directly to the wellhead, as for mounting a blowout preventer, or it may connect indirectly to the wellhead, as via a flow line. Examples of such indirectly connected devices are: tree cap and re-entry connectors, split tree connectors, flow loop connectors, flow line connectors, and production riser connectors.
Such a connector typically includes an annular main body which is connected in coaxial alignment with the subsurface wellhead or another body in turn connected to the wellhead. The connector body carries some type of latch means which can be extended and retracted, usually by a generally radial movement, for engagement and disengagement with the wellhead so as to connect or disconnect the connector main body thereto. In most such connectors, these latch means are actuated or moved into their radially extended positions for engagement with the wellhead or other body by a longitudinally reciprocable actuator. The actuator may, for example, comprise some type of piston means which directly, or indirectly via another member movable therewith, cams the latches radially inwardly as the piston means is extended in a longitudinal direction. When the piston means is moved in the opposite longitudinal direction, the latches are freed for radially outer movement so that the connector can be removed.
After such an actuator has been extended, to in turn extend the latches and thereby engage the wellhead or other body, it is desirable to mechanically lock the actuator and latches in their extended positions so that hydraulic pressure need not be maintained on the actuator in order to maintain the latching engagement.
In the past, numerous systems have been devised for achieving such mechanical locking. In most cases, the locking assembly would include at least one member movable longitudinally jointly with the actuator with respect to the main body of the connector or an attachment thereto. The adjacent portion of the connector body or attachment would have carried thereon some type of retainer means engagable with the aforementioned movable portion of the locking assembly to mechanically restrain it from subsequent longitudinal movement. Although the retainer means of such an assembly might initially be hydraulically activated, it would be designed to interlock with the movable member, e.g. by opposed shoulders, so that the actuating pressure could be released without releasing the retainer means from engagement with the movable portion of the locking assembly.
Such prior locking assemblies have suffered from several disadvantages. In the first place, the interlocking formations which permitted the retainer portion of the locking assembly to remain in its locking position in the absence of hydraulic pressure would also necessitate some type of mechanical forcing of the retainer means into a retracted position, e.g. by a camming action, when it was desired to remove the connector. Thus, such prior locking devices were susceptible to jamming and other problems, which in turn required expensive and time-comsuming use of divers and/or destruction of at least a part of the connector in order to remove it from the wellhead. As mentioned, such prior devices have included some type of special formation on the movable portion of the locking assembly which formation could be engaged by the retainer means carried by the connector body. Such an engagable formation was necessarily located in some fixed position along the length of the movable portion of the locking assembly. The problem with this arrangement is that, in connecting a connector to a subsea structure such as a wellhead, it is not always possible to predict or accurately control the amount of extension of the latches and actuator which will be permitted. For example, the profile of a wellhead which is designed to mate with connector latches may be effectively altered by wear, corrosion, debris, or the like so that more or less than the ideal amount of latch travel is needed, or indeed possible, for latching of the connector to the wellhead. Since the amount of longitudinal travel of the actuator corresponds to the amount of radial travel of the latches, it is therefore difficult and expensive to attempt to ensure that the engagement formation of the movable portion of the locking assembly, which moves jointly with the actuator of the connector, will be properly aligned with the retainer means when the actuator has moved downwardly as far as possible.